Telephone system



Auggl'S, 1942. G. L. cAlN ET AL 2,293,538

TELEPHONE SYSTEM Filed April 18, 1941 2 Sheets-Sheet 2 lll ROT TIM/NG CIRCUIT G. L. CA/N /NVEA/TORS: E. `SM/ 7' H H A. SOUCY Patented Aug. 18, 1942 UNETED STATES PATENT OFFICE TELEPHONE SYSTEM Application April 18, 1941, Serial No. 389,138

Claims.

'I'his invention relates to telephone systems and particularly those in which conversational connections are established by automatic switches.

The objects are to improve the releasing operations of partly established connections, test the condition of connectors from which a trouble signal has been given and other connectors serving telephone connections without interfering with established connections and otherwise improve such systems.

Systems have been devised heretofore in which the immediate release of all switches of the connection takes place when the calling subscriber replaces his receiver and in which release of the nal or connector switch is effected at the end of a measured interval following the replacement of the called subscribers receiver providing the calling party is slow in hanging up his receiver. Moreover it is common practice to employ the relay of the connector that responds to the called subscribers switchhook not only for the purpose of controlling the release circuits but also to effect a reversal in the direction of current flow in the established connection for supervision.

A feature of the present invention is an improvement in these prior systems which consists in testing the condition of a switching connection and in causing a responsive action in a testing circuit to a plurality of different switching connection circuit conditions for either releasing said switching connection or for stepping off of said switching connection when the circuit condition encountered does not warrant the release of the connection.

Another and related feature consists in repeating the test of the switching connection until a trouble is cleared.

Another and related feature consists in the use of a vacuum tube circuit responsive -to current sources associated with the line conductors for controlling the testing circuit responsive to different conditions encountered in a connector switching circuit.

The foregoing and other features of the invention will be described more fully in the following specication which should be taken in conjunction with the accompanying drawings and also the appended claims:

Referring to the drawings, Fig. 1 illustrates a calling subscriber lill connected to a called subscriber i it by a line nder switch, a rst selector, a second selector and a connector. The line finder and selectors are diagrammatically shown and may be of any suitable type such as the Stlowger switch, the operation and release of which are well known. Figure 1 also illustrates the commutator and a horizontal level of a connector switch testing circuit and the brushes associated therewith. Fig. 2 illustrates a connector switch testing circuit and Fig. 2A illustrates the essential apparatus of a trouble indicating circuit cooperatively associated with the testing circuit, Fig. 2 and the connector circuit, Fig. 1.

In general the telephone system to which the invention applies is known as the step-by-step telephone switching system wherein after a telephone connection has been completed from a calling to a called subscriber through a line finder, rst selector, second selector and connector, the calling subscriber controls the release of these switches after the conversation has ceased. The failure of the calling subscriber to replace the receiver on the switchhook therefore holds this train of switches in an operated position and prevents the called subscriber from making further calls until such time as the connector is released. When a connector is held by the calling subscriber and the called subscriber has replaced the receiver on the switchhook or is held in an operated position by a fault in the connector, a circuit is established in the connector for actuating what is known as a permanent signal shelf alarm circuit. The actuation of the alarm circuit lights a lamp to indicate that a connector is being held by a calling subscriber or by a fault in the connector or the associated circuits and normally after an interval yof time an alarm is sounded.

According to the present invention the energization of the permanent alarm circuit actuates a testing circuit and causes the testing circuit to associate itself with the connector in trouble by the operation of a step-by-step switch. The Vertical movement of the testing circuit step-by-step switch is arrested by a ground on a segment of the switch commutator which ground is connected therewith by an alarm circuit actuated by a connector switch in the corresponding horizontal level. The rotary movement of the brushes is under the control of the testing circuit in which any of a plurality of circuit conditions may be established depending upon the circuit condition found to prevail in the connector tested. Assuming that the connector giving the alarm is connected to a set of `terminals in the middle of the horizontal level it is then necessary for the testing circuit brushes to pass over other terminals to reach the connector in trouble. The testing circuit may therefore encounter other connectors which are in different normal operating conditions, either having completed a telephone connection from a calling subscriber to a called subscriber or are in the process of completing such a connection. The testing circuit is arranged to respond to the dilerent conditions found in connectors. As the testing circuit brushes advance around the terminal bank, the conditions to be encountered on the various sets of terminals in the horizontal row may be as follows:

1. A normal release connector, i. e., not in. use for a service connection and not associated with a trouble condition.

2. A connector being used for a conversational connection.

3. A connector associated with a called subscriber with ringing current actuating the called subscribers ringer.

4. A connector associated with a busy line and transmitting a busy tone to the calling subscriber.

5. A connector associated with an intercepting operator.

Any of the above conditions are recognized by the devices of the testing circuit which cause the testing circuit to advance its associated switch brushes without disturbing the normal functioning of the connector encountered.

If the testing circuit is associated with a connector which is being held by a calling subscriber and the called subscriber has replaced the re- ,Y

ceiver on the switchhook, the testing circuit actuates the connector release mechanism which restores the connector mechanism to normal and restores the preceding switches to normal which were actuated for making the telephone call. Other conditions are caused by the varied actions of the calling and called subscribers which if not taken into consideration might create dissatisfaction and annoyance to some subscrib-ers even though these conditions may be unusual in normal telephone usage or telephone practice. For example, a circuit in a connector may be established for actuating the testing circuit and when the testing circuit switch brushes are associated with this connector a telephone connection may have been established between a calling and a called subscriber or the connection may be in the process of being established. Under this condition the testing circuit switch brushes are stepped off of the terminals of the connector which gave the alarm. If the trouble condition persists rep-cated tests may be made until the conversation is terminated and the trouble is found.

A detailed description will first be given of the connector circuit, Fig. 1, followed by a description of the testing circuit Fig. 2, the trouble circuit Fig. 2A and the relation of the circuit conditions found in the connector to the responsive action in the testing circuit.

Let it be assumed that the subscriber of line |0| desires to establish a connection with the station ||0 and that the connection has been eX- tended in the usual manner through line finder LF and selectors SI and S2 to the tip, ring and sleeve terminals of connector C. When this circuit is seized by the selector S2 a circuit is closed through the windings of relay |03 which may be traced from battery through the lower winding of relay |03, normally closed contacts 2 of relay |04, ring terminals and brushes of selectors SI, S2, and the line nder LF, thence over line conductor M5 and through subscribers telephone l5! and dial |02, over conductor H6 and through tip terminals and brushes of line nder LF, and selectors Si and S2, normally closed contacts of relay |03 landupper winding of relay |03 to ground. Relay |03 operates which operates relay H1 through a circuit traceable from battery through the winding of relay to ground on the Contact of relay |03. Relay Hl in operating connects ground on its contact 3 to the sleeve conductor |35 and the sleeve terminals and brushes of selectors SI, S2 and line finder LF, thereby holding in the operated position the selectors and line finder and guarding connector C from other hunting selector circuits.

On the rst break of the contacts of dial |02 for the purpose of dialing the tens digits of the called number, relay |03 releases and closes a circuit from battery through the windings of Vertical magnet |20 and relay H9, lead |22, contact of the Vertical olf-normal contact assembly |2|, contact 2 of relay to ground on the contact of relay |03. Relay is slow to release and does not release during the momentary open periods of the front contact of relay |03, while responding to the pulses of dial 02. Relay i3 and vertical magnet |20 are operated through the circuit hereinbefore retraced. As soon as the shaft of the connector switch is moved from its normal position on its rst vertical step, the vertical o-.normal springs |2| operate and transfer the operating circuit for relay ||9 and vertical magnet |20 from conductor |22, to conductor |23, thereby placing the windings of relay I9 and vertical magnet |20 in series through the make Contact of relay H9, and contact 2 of the vertical oiF-normal spring combination |2|. 'I'his transfer from conductor |22 to |23 is made without interrupting the circuit, since the three upper springs of combination [2| are of the makebefore-break type. When the contacts of dial |02 are closed again after the rst break, relay |03 reoperates and again closes the circuit through the winding of relay before this relay has had time to release, as hereinbefore explained. On the next open period of dial |02, relay |03 again releases and transmits a second ground pulse, through the circuit of relay 9 and vertical magnet |20. Relay ||9 is slow to release and remains locked up over the open periods of the back contacts of relay |03. The second ground pulse aforesaid causes the shaft of the switch to take another step upward. This action continues until all required pulses for the tens digits are transmitted by dial |02 and the connector brushes ||2, ||3 and l I4 have reached the level containing the terminals of the line being called.

After the tens digit has been dialed and dial 02 is restored to normal, relay |03 remains operated, relay ||9 releases, and the winding of vertical magnet |20 is deenergized. When relay H9 releases, a circuit is closed through rotary magnet |24 for rotary stepping and a circuit is closed for relayv |25. These circuits may be traced from battery through the winding of rotary magnet |24, contact 6 of relay |23 to junction point |29, and from battery through the winding of relay |25 to said junction point |29, thence through the upper contact of relay |30, back contact of relay 9, over conductor |23, contact of combination 2| to contact 2 of relay On the rst break of dial |02 for dialing the units digits of the called number, i. e., for rotary stepping, relay |03 releases and connects a ground impulse to contact 2 of relay 'l and over the rotary stepping circuit just traced. Relay 'l remains operated during dial pulses, as in the case of vertical stepping. In response to said rst ground impulse rotary magnet |24 lwill operate and cause the switch brushes |2, H3 and i4 to rotate one step in a horizontal direction. Relay |25 operates to short-circuit the upper contacts of relay I |30 to maintain the above circuit closed if relay |30 momentarily operates. Subsequent dial pulses cause rotary magnet |24 to step the switch around until the line H of the called subscriber is reached.

When dial |02 has restored to normal the circuit for relay and the rotary magnet |24 is opened since relay |03 remains operated. Slow relay |25 does not release at once. Before connecting ringing current to this line a test is made to determine whether the line is busy or idle. If the called subscriber line is busy, ground |45v Will be found on the sleeve terminal connected to conductor |38, and will cause the operation of test relay from battery through its winding, contact 2 of relay |23, contact 2 of slowrelease relay |25, conductor |44, to ground |45 on sleeve conductor |08 through brush ||4. Relay |30 in operating opens the original circuit for rotary magnet |24 and when slow-release relay |25 finally releases the second circuit established for rotary magnet |24 is opened and a holding circuit is established for relay |30. Relay |30 in operating connects the secondary winding of busy tone transformer |33 through its contacts 3, ring conductor |34, condenser |55, ring conductor of selectors 2 and and the line nder to the calling subscribers station, which indicates to the calling subscriber that the called line is busy. Relay |30 is locked up through a circuit traced fromy battery through the winding of relay |30, contact 2 of relay |23, contact 2 of relay |25 released, contact 2 of relay |30 to ground on sleeve conductor |35. Under this condition the calling subscriber will disconnect, causing the release 0f relays |03 and thereby closing a circuit from battery through the Winding of release magnet I8, contact 2 of VON combination |2l, contact 3 of relay |28, contact 2 of relay and contact of relay |03 to ground. Release magnet |93 is energized and causes the restoration of the connector switch to normal, including VON springs |2|. Relay |30, which was locked to ground on sleeve conductor |35, releases since ground was removed by the opening of Contact 3 of relay when this relay released. The removal of ground from conductor |35 causes in the well-known manner the energization of release magnets |30, |3| and |62 of the preceding switches and the consequent release of these switches.

Let it be assumed now that the line ||0 of the called subscriber is found idle. Under this condition battery will be found by sleeve brush ||4 on the terminal connected to sleeve conductor |08 through the Winding of cut-off relay |46. Under this condition relay |30 will not operate as hereinbefore described when the line ||0 was found busy. After relay |25 has released upon the completion of rotary stepping, a circuit is closed for the operation of relay |28, which may be traced from aforesaid battery connection on brush Ii 4, through contact 2 of relay |25, lower winding cf relay |28, contact 2 of relay |30, to ground on sleeve conductor |35. operating locks through its upper winding and its Contact 4 to ground on contact of relay In operating relay |28 also connects tip conductor |38, through its Contact i to ground on contacts of relay |39; opens the circuit of the winding of relay |30, by opening its contact 2; connects ground from pick-up interrupter |40 through its contact 5, contact of relay |4|,

Relay |28 in contact 3 of relay |39 to battery through the winding of relay |4|. Relay |4| operates and locks through its contact l to ground on contact 3 of relay lil. Relay |28 in operating also opens the lead to the rotary magnet |24 through its contacts 3; connects ring conductor |42 to ring conductor |43 through its contact and joins sleeve conductor |35 to sleeve conductor |44, thereby grounding said conductor |44 for operating cut-off relay |43, and guarding the terminals of the line of subscriber H0 from seizure by another connector.

When relay |4| operates it closes a circuit for ringing the station H0. This circuit is traced from source of ringing current |41, which may comprise an interrupter connected with an alterhating-current generator and with battery on diierent segments, through contact 2 of relay |4|, lower` winding of relay |39, contact 4 of relay |30, over conductor |43, contact 1 of relay |28, conductor |42, through connector brush ||3 and associated contact, over the line of subscriber H0, connector brush ||2 and associated contact, conductor |38, contact of relay |28, to ground on contact of relay |30. The ringer (not shown) of station H3 is now actuated, but relay |30 does not operate until subscriber i0 answers by removing the receiver from the switchhook, thereby removing the ringer winding from the circuit and connecting a low impedance bridge across the line. Ringing tone is sent back t0 the calling subscriber over conductor |34 during the periods when ringing current is connected with station H0. The contacts of relay |33 are adjusted so that in operating a locking circuit is closed from battery through its upper winding and contact 2 to ground on contact of relay Ill before the circuit through its lower winding is broken at either of its contacts or 4. The operation of relay |39 disconnects ringing current from subscribers station H0. The locking circuit for relay |4| is also opened causing the release of the latter relay to disconnect the ringing source |42. In some instances the called subscriber such as the subscriber at station l0 may remove his receiver to make a call after a connector has been connected to his line, but before relay |4| has been operated by pick-up interrupter |40. To guard this condition a circuit is provided to operate relay |39 before ringing current is applied to this called station. lThis circuit may be traced from battery through contact 2 of relay UH, lower winding of relay 633 and thence over the line conductors as traced through station l0 to ground on contact i of relay |33. Under this condition the locking circuit for relay |30 is established through its upper winding in the same manner as previously described.

The conversational circuit between the calling and called subscribers is completed by relay |39 by closing through the tip conductors on its contact I, and the ring conductors on its contact 4. Relay |39 in operating also completes the operating circuit for relay |04, which may be traced from battery through the upper winding of relay 504, contact of relay |33, cont-act of relay |28, over the tip conductor |35 and the line of station ||0, through station |i0 including dial Hi, ring conductors of the line, conductor |42, contact of relay |28, contact 4 of relay E30 to ground through the lower Winding of relay |04. Relay |04 in operating reverses the direction of current over the line of calling station |0I, thereby causing the operation of an associated line message register (not shown) in the well-known manner.

After the aforesaid reversal, battery through the lower winding of relay |03 is connected by contact I of relay |04 to the tip conductor, and ground through the upper winding of relay |03 is connected by Contact 2 of relay |04 to the ring conductor.

At the end of the conversation, when the calling subscriber disconnects, relays |03 and I I1 release, removing ground from the upper locking windings of relays |39 and |28, which release. The release of relay |28 closes a circuit for operating release magnet I I8, which may be traced from battery through the winding of magnet IIB, contact 2 of VON combination I2I, contact 3 of relay |28, contact 2 of relay l1, and the contact of relay |03 to ground. The operation of release magnet I i8 restores the connector switch to normal in the well-known manner. The removal of ground from conductor |35 causes the operation of release magnets |50, |6I and |02 and the immediate release of the preceding switches LF. SI and S2.

The connector switch operates satisfactorily in the manner outlined above unless equipment becomes out of adjustment through carelessness of a maintenance man or when a calling subscriber fails to replace the receiver on the switchhook when a telephone conversation is terminated and the called subscriber has replaced the receiver or when an attempt has been made to connect a calling subscriber with a called subscriber and the called subscriber does not answer or the line has been found busy. As outlined above, the release of the connector and the preceding switches LF,

SI and S2 is under the control of the calling l subscriber IlI since relays |03 and |I1 must release in order to establish a circuit for release magnet l IS. When a connector is not released by the calling subscriber, the called subscribers line is maintained busy and this subscriber cannot obtain connection with other telephone lines until this connector has been released. Assuming that this condition prevails, certain apparatus in the connector circuit will be in the following operated or released positions. Relay |04 is released since this relay is under the control of the called subscriber who has replaced the receiver on the switchhook. Relay |03 would remain operated since the subscriber at station |I has not replaced the receiver on the switchhook and consequently a circuit is established for this relay through switches Sl, S2 and LF over the subscribers loop. Relay I 03 holds relay II1 operated and a holding circuit is maintained for relays I39 and |28 through the upper windings of these relays to ground on contact I of relay III1. Under this condition, a supervisory circuit is established to energize a, permanent signal timing circuit shown in Fig. 2A. This circuit may be traced from ground through contact 3 of relay |04, contact 5 of relay |39, filament of lamp 245 in parallel with resistance 250, contact 2 of relay 2I3, left winding of relay 2I8, tuning circuit pick-up interrupter (not shown), to battery in the timing circuit. The high resistance of the left winding of relay 2I8 prevents the illumination of lamp 245 at this time. The energization of relay 2|8 causes the closure of a timing circuit which actuates diierent equipment after diierent time intervals have elapsed and will ultimately energize an audible alarm after a comparatively long time interval to indicate that the connector and preceding switches are held in an operated position. This timing circuit is diagrammatically shown and may be any timing circuit well known in the art.

The testing circuit Fig. 2 is shown arranged for association with a plurality of connectors C which are connected by multiple wiring to the T, R and S terminals of the horizontal levels, such as |12 of the testing switch and the connectors which are so wired to a terminal level would ordinarily be mounted on the same shelf of an equipment frame. The testing circuit is thus associated with a plurality of shelves of connectors and may be energized by any of these connectors over .a circuit extending from a connector to the electrical equipment shown in Fig. 2A. One lamp 245 is provided for each connector. Relays 2|4 and 2I8 are provided for each shelf of connectors. The commutator |10 of the testing switch has one segment for each shelf of connectors. Relay 244 may be common to a complete frame of connectors and the timing circuit may be common to a plurality of frames of connectors.

In accordance with the present invention this timing circuit is employed to energize the connector test circuit after a short time interval by rst energizing relay 244. This relay associates ground through resistance 259 and its contact I, contact I of relay 2I8, winding of relay 2I4 to battery energizing relay 2I4 in the shelf alarm circuit. The energization of relay 2I4 associates battery through the winding of the test circuit start relay 2I3 to ground. Relay 2I4, in operating, establishes a locking circuit for itself to ground on contact 3 of connector relay I 04 through lamp 245 and resistance 258. The winding of relay 2 I4 is of low resistance and causes the illumination of lamp 245. The locking Vcircuit for relay 2I4 is established in this manner so that if at any time when the test circuit is functioning, the connector ground is removed from the test circuit, the testing circuit will restore to normal. With test circuit start relay 2I3 energized, a circuit is established for relay 2I0 from ground through contact 2 of relay 2I3, winding of relay 2I0, contact 2 of normally operated relay 242 to battery. Relay 2| 3 also establishes a circuit from battery through its contact I, contact I of relay 2I2, contact of rotary magnet 200, winding of relay 206, winding of relay 205, contact of Vertical magnet 201, winding of relay 2II to ground. Relays 205 and 206 are marginal and do not operate in the circuit traced. Relay 2| I operates for energizing the Vertical magnet 201 a circuit for which may be traced from ground through the contact of relay 2II, winding of vertical magnet 201, contact 5 of relay 2I0 to battery on contact 2 of the normally operated relay 242, Relay 2 I0 connects leads 260, 26|, 252 and 263 from the tube circuit to the testing relays and to the testing circuit switch brushes 254, 255 and 256 for indicating different conditions encountered in connector circuits as described later. The energization of vertical magnet 201 causes the elevation of commutator brush I1I and the tip, ring and sleeve brushes 254, 255, and 256. The brush I1I seeks a terminal on a level I to I0 which has been associated with ground by the connector shelf alarm signal circuit. This ground may be traced from contact of relay 2I8 to the commutator segment associated with the tenth horizontal level. When the vertical magnet 201 attracts its armature, the circuit for relay 2H is opened causing its release. The release of relay 2II opens the circuit for vertical magnet 201 causing its release and relay 2I| thereupon reoperates to reenergize the Vertical magnet 201. The alternate operation and releases of the vertical magnet and relay 2II continues until ground is encountered on one of the commutator terminals. A circuit is shown from ground through the tenth segment of commutator |10 and brush |1I to a point between the winding of relay 2| I and the windings of relay 205. This ground shunts relay 2| I causing its release which opens the circuit for the vertical magnet 201. This ground also increases the current flow through relays 205 and 205 to cause the operation of the marginal relay 205. In the above example, this ground was encountered on commutator segment I which shunted relay 2|| and arrested the further operation of the vertical magnet 201. This ground may be encountered on any one of the segments I to I0 which would arrest the operation of the vertical magnet when brush I1| reaches this commutator segment and brushes 254, 255 and 256 reach the corresponding horizontal level of the connector switch terminals such as |12. The operation of relay 205 establishes a circuit for the rotary magnet 200 which may be traced from ground on the contact of relay 205, winding of rotary magnet 200, contact 5 oi relay 2 I0 to battery on contact 2 of relay 242. The energization of the rotary magnet causes the progression of the brushes 254, 255 and 256 over the tip, ring and sleeve terminals of connectors which are wired to these terminals.

Let it be assumed that connectors of the type shown in Fig. 1 are wired to the sets of terminals of the tenth level |12 and that the connector wired to one set of these terminals has given an alarm signal. Any of these connectors may be in use and as previously shown the removal of the switehhook in the calling station causes relays |03 and ||1 to be energized and consequently ground is associated through contact 3 of relay ||1 with sleeve conductor |35 and with the sleeve terminal of the connector. The operation of rotary magnet 200 in making its iirst step dissociates its armature from its contact which opens a circuit for relay 205 causing its release. The release of relay 205 releases the rotary magnet 200 which reestablishes the operating circuit for relay 205 unless ground is connected to the sleeve terminal of contact set No. I by the connector wired to this set of terminals. If ground is encountered on the sleeve terminal a circuit is established from this ground through brush 255, contact of relay to a point between the winding of relay 205 and the winding of relay 205 which releases relay 205 arresting the action of the rotary magnet and causes the operation of marginal relay 205. If the connector wired to a set of terminals is idle and no ground is encountered on the sleeve terminal, relay 205 is reoperated which reenergizes the rotary7 magnet for moving the brushes another step. When relay 205 is operated it establishes a circuit from ground through its contact, winding of relay 204, contact 5 of relay 2I0, to battery through Contact 2 of relay 242 which operates relay 204.

Calling party permanent The testing circuit is arranged to function in different manners responsive to different conditions which may be found in each connector switching circuit encountered by the testing switch brushes. As .previously stated, the .permanent signal shelf alarm circuit may be actuated when a calling subscriber has not replaced the receiver on the switchhook whereas the called subscriber has replaced the receiver and the testing circuit responds to this condition to cause the release of this connector. A time interval is usually provided before the testing circuit acts to release the connector. For this purpose the releasing circuit is established through an interrupter such as interrupter 241 for operating relay 202 after the operation of relay 200. The circuit for relay 202 may be traced from battery, through the contact of interrup-ter 241, Winding or relay 202 to ground through the contact of relay 206. The energization of relay 202 connects ground to the tip conductor and battery to the ring conductor of the calling line loop which shunts relay |03 and causes its release. This circuit may be traced from ground through the upper winding of relay |03, contact I of relay |04, brush 254, lead 25|, contact I of relay 202, contact I of relay 203 to ground. The circuit from battery through the lower winding of relay |03 may `be traced through contact 2 of relay I 04, ring brush 255, conductor 2152, contact 2 of relay 202, contact 2 of relay 203, contact I of relay 243, winding of relay 243 to battery. Relay 243 is a low resistance marginal relay for use with either comparatively short subscribers loops or long subscribers loops. The operation of relay 202 also establishes a circuit for relay 2|2 traced from ground through contact 3 of relay |51, lead |35, brush 256, conductor 253, contact of relay 20|, contact 3 of relay 202, contact 3 of relay 203, winding of relay 2I2 to battery. Relay 2|2 establishes a locking circuit for itself through its contact 3 to ground on contact 2 of the vertical oit-normal springs 2I1.

When relay |03 is caused to be released by shunt, the circuit for relay I|1 is opened causing the release of this relay and the release of relays |39 and |28 since the holding' circuits through their upper windings has been opened by the release of relay II1. The release magnet IIS is thus energized for releasing the connector over a circuit from battery through the ywinding of release magnet I I3, contact 2 of Vertical oli-normal springs |2I, contact 3 of relay |23, contact 2 of relay |I1 to ground on the Contact of relay |03. The removal of ground from conductor |35 causes the energization of release magnets |50, I5I and |62 for the release of the line nder, selector I and selector 2, respectively, in the manner well known in the art. The release of the connector removes ground from sleeve brush 255 which removes the shunt ground from the junction point between the windings of relays 205 and 205 causing the reoperation of relay 205 and the release of the marginlal relay 200. Relay 205 is operated over a circuit from battery through Contact I of relay 2|3, contact I of relay 2I2, contact of the rotary magnet 200, winding of relay 205, winding of relay 205 to `ground on the rotary off-normal contact and to ground through brush I1|. The operation of relay 205 extends ground through the winding of the rotary magnet 200, contact 5 of relay 2|0, contact 2 of relay 242 to battery. The operation of rotary magnet 200 causes the release of relay 205 which releases the rotary magnet causing relay 205 to again operate which continues until the Ibrushes 254, 255 and 255 reach the 11th rotary step. The release of relay 200 opens the circuit for relay 202 which releases. When the testing circuit switch brushes reach the 11th rotary step ground is connected through springs 2|5, winding of relay 2|2 to battery operating relay 2 i2 which locks through its contact 3 to ground on the vertica1 orf-normal contact 2H. The operation 0f relay 212 establishes an energizing circuit for relay 209 from ground through its winding, contact 2 of relay 2|2, contact 4 of relay 202 to battery. The operation of relay 200 connects ground through its contact, winding of release magnet 208 to battery causing the release of the testing circuit switch.

Called subscriber answers In the above circuit traced for shunting the winding of connector relay |03 to cause its release and the release of the connector switch, battery was connected through the lower winding of relay |03 and the contact of relays |04 and 202, thence through the winding of relay 243 to battery. Relay 203 does not operate in this circuit, but if the subscriber at station ||0 should remove the receiver from the switchhook before or approximately at the same time that relay 202 is operated the condition is altered by the operation of relay in response to the removal of the receiver in station ||0. This is the same condition found by the testing circuit when it is associated with a connector in normal use for a conversational connection between a. calling subscriber and a called subscriber but since the circumstances are different a different circuit combination is formed in the testing circuit as later described. The operation of relay |04 reverses the current from the windings of relay |03 through the contacts of relay |04 over the calling subscribers loop and to the tip and ring test rushes 254 and 255 in the testing circuit, causing the operation of relay 203 which locks to ground on the vertical off-normal springs 201. The operation of relay 243 opens the battery circuit extending through its winding to the ring conductor of the connector circuit and operates relay 20|. Under this condition the connector relay |03 does not release and the testing circuit rotary stepping magnet 200 is energized to move the testing circuit brushes off of the connector terminals. The operation of relay 20| disassociates the connector sleeve ground from the junction point between relays 206 and 205. The removal of this ground causes relay 206 to release and relay 205 to again operate over a circuit from battery through contact I of relay 2|3, contact l of relay 2|2, contact of the rotary magnet 200, winding of relay 206, winding of relay 205 to ground on the rotary off-normal contact and to ground through brush lll and commutator I0 which is placed thereon by contact I of relay 2|8. The operation of relay 205 extends ground through the winding of the rotary magnet 200, contact 5 of relay 2li), contact 2 of relay 2&2 to battery. The operation of the rotary magnet 200 causes the release of relay 205 which releases the rotary magnet causing relay 205 to again operate which continues until the brushes 254, 255 and 250 reach the leleventh rotary step if another connector in an off-normal condition is not encountered on terminals between the released connector and the eleventh rotary step. The release of relay 205 opened the circuit for relay 202 which released. When the brushes reach the eleventh rotary step, ground is connected through spring 2| 5, winding ofA relay 2|2 to battery operating relay 2|2 which locks through its contact 3 to ground on the vertical off-normal contact 2H. The operation of relay 2|2 establishes an energizing circuit for relay 209 from ground,

through its winding, contact 2 of relay 2|2, contact i of relay 202 to battery. The operation of relay 209 connects ground through its contact, winding of release magnet 208 to battery causing the release of the testing circuit switch.

Repeated test rI'he foregoing restoration of the testing circuit switch took place so as to cause no interference between subscribers who may want to continue conversation. The circumstances may, however, be such that the alarm signal circuit is again actuated by the time the testing circuit has restored to normal. For example, the subscriber at |0| may have the receiver off the switchhook and the subscriber at H0 may'have attempted to make another call to a diierent subscriber. After failing to obtain service the subscriber at H0 may have replaced the receiver on the switchhook which would again restore relay |04. Under this condition relays |03, H1, |39 and |28 would remain operated and ground would be associated through contact 3 of relay |00, contact 5 of relay |39 to either maintain relays 280 and 2| 0 operated or reoperate relay 2|S which would reoperate relay 2M. Under this circumstance, relay 2| 3 is operated which actuates the testing circuit to repeat the test of this connector switch. The circuit previously traced for the vertical and rotary magnets is again established from battery through contact of relay 2|3, contact of relay 2|2 which has restored to normal, contact of rotary magnet 200, winding of relay 205, winding of relay 205, contact of Vertical magnet 201, winding of relay 2H `to ground which energizes relay 2|| as previously described. Since relays 205 and 205 are marginal they do not operate in the circuit traced and the Vertical magnet is energized through the contact of relay 2| l. The circuit operations proceed as previously explained to elevate brushes 250 255 andl 255 to the terminals of the connector giving the alarm signal. On this repeated test, if the subscriber ||0 has replaced the receiver on the switchhook and subscriber 0| has not, relay |03 is released by shunt as previously described. The connector is released causing the release of the associated line nder, selector l and selector 2 which causes the release of the testing circuit. f

Conversational connection Under some circumstances the shelf alarm signal circuit is actuated and the testing circuit switch brushes are elevated to the terminal level containing the connector giving the alarm but upon reaching this level connectors are encountered over which conversation is taking place between two subscribers. This condition is different from therone previously described under the subheading of (Calling party permanent) since suinci'ent time does not elapse for relay 202 to operate. It will be remembered that relay 206 is energized when ground is encountered on the sleeve of the connector, which under this condition is connected thereto through Contact 3 ofV relay lili, and that the circuit for relay 202 is established from battery through the interrupter 241, winding of relay 202 to ground on relay 205 for releasing relay |03. But with conversation taking place between subscribers over the connector, the following circuits are established which causes the testing circuit switch to step its brushes 25s, 255 and 250 01T of the terminals associated with this connector before the circuit of relay 292 is connected through the contact of.`

interrupter 241. This circuit involves tube 220 and it should be noted that this tube circuit is arranged for normally creating a plate current to energize relay 2|9, which maintains relay 20| normally released. A connector in use for telephone conversation has both relays |04 and |03 operated and consequently battery through the lower winding of relay |03 is extended to the tip terminal of the connector over the calling subscrbers line loop to ground through the upper winding of relay |03. A circuit is established from this battery through switch brush 254, Contact 2 of relay 2 I0, lead 200 to a junction point between resistances 22| and 222 in the circuit wiring of tube 220. Since the battery connected to relay |03 and the battery connected to tube 220 are of the same voltage this creates a negative bias on the grid circuit of tube 220 which suciently reduces the plate current through the winding of relay 2|9 to cause the release of the latter relay. The operation and release adjustments of relay 2|9 are so arranged that this relay may be released by a certain percentage reduction in the plate current. It is recognized that the potential impressed upon the sleeve terminal of the connector through the lower winding of relay |03 will vary to some extent depending upon the length of the line loop.

The release of relay 2|9 establishes a circuit v from ground, through its contact, contact of relay 2|0, winding of relay 20| to battery which operates relay 20|. The operation of relay 20| opens the ground circuit which had been established from the sleeve of the connector placed thereon through contact 3 of relay ||1 which extends through brush 256 to a junction point between relays 205 and 206. The operation of relay 20| thus causes the release of relay 205 and the energization of relay 205. As previously described, this establishes a circuit for the rotary magnet from ground on the contact of relay 205, through the winding of rotary magnet 200, contact 5 of relay 2|0 to battery on contact 2 o1 relay 242. The brushes 254, 255.and 256 may be rotated to the eleventh rotary step if another offnormal connector is not encountered and a circuit is established for relay 2|2 from ground on springs 2|5, Winding of relay 2|2 to battery. The operation of relay 2|2 energizes relay 209 and the energization of relay 209 establishes a circuit v for the release magnet 208 in the manner previously described.

It is possible that a fault may be present in the connector giving the alarm and that this fault continues to be present after the conversation has ceased between subscribers using the connector when the rst test was made. A fault of this character may occur through carelessness of a repair man who may have dropped solder causing a cross between contacts which does not prevent the use of the connector but which may create a condition to give a permanent alarm signal. Under this circumstance, the testing circuit repeatedly establishes connection with the connnector and when conversation over this connector has ceased it may seize the connection and give an alarm after a timed interval.

Busy called lines or no answer Other conditions may be encountered in connectors which have been directed b y a calling party to a busy line or to a called party such as ||0 who has not answered by removing the receiver from the switchhook. Under these circumstances, either an audible ringing tone is found on the ring conductor of the calling line or a busy tone is found on the ring conductor of the calling line when the testing switch brushes reach the terminals wired to the connector. Under this circumstance, the testing circuit may have been energized in the manner previously described and associates the tip, ring and sleeve brushes 254, 255 and 250 with the connectors in a switch bank. The foregoing conditions are automatically recognized by the testing circuit. The tone circuit may be traced from the ring conductor of the connector over testing circuit brush 255, conductor 252, contact 3 of relay 2i0, conductor 26|, condenser 226 to the grid of tube 223. This busy tone or audible ringing tone is fed from a current source in the form of alternating or pulsating current which is amplied and placed across tube 236. Tube 235 recties this current and applies direct current voltage to tube 240 for diminishing the plate current iiow through the winding of relay 24| causing the release of the latter normally operated relay. This connects ground through the contact of relay 24i, contact of relay 2|0, winding of relay 20| to battery which operates the latter relay to open the ground circuit extending from the sleeve conductor of the connector switch circuit to the junction point between relays 205 and 206. This causes the release of relay 206 and the reoperation of relay 205 for reactuating the stepping circuit of the testing switch in the manner previously described for stepping the test brushes to the next set of terminals. Any oli-normal connectors encountered actuate the testing circuit as described herein and the testing circuit is restored to normal when the test switch brushes reach the eleventh rotary step.

Relay 242 is normally operated from battery supplying current to the tubes. The release of this relay indicates a battery failure by establishing a circuit for the alarm bell 249.

I ntecepting operators trank The testing circuit may encounter a connector which is associated with an intercepting operators trunk circuit having been routed thereto from a calling subscriber who called for a telephone line which no longer existed. The intercepting operators circuits are arranged for conversational connections with a calling subscriber through the equipment of a connector without operating connector relay |05 in order to prevent the operation of the message registered in the calling subscribers line. This connection, therefore, presents the same circuit conditions to the testing circuit as a connector which is held by a calling subscriber after the called subscriber has replaced the receiver on the switchhook. The intercepting operators trunk is, however, arranged to transmit a tone over the sleeve conductor, as shown, in place of the usual sleeve ground. This tone is transmitted to the testing circuit over a circuit which may be traced through the secondary winding of transformer |75, sleeve terminal |03, brush H4, contact 8 of relay |23, conductor |35, sleeve terminal associated with test brush 256, Contact 4 of relay 2|0, conductor 262, condenser 232 to the grid of tube 230. Tube 235 is arranged to rectify this current and apply the rectifying current to tube 240 causing the release of relay 24|. The release of relay 24| connects ground through contact of relay 2|0, winding of relay 2I0 to battery for operating the latter relay. The operation of relay 20| immediately opens the circuit extending Ifrom the sleeve of the connector switch to the False ground If a false ground is present on the sleeve conductor of a connector the testing circuit remains associated with the connector for a sufficient time to cause the operation of relay 2E? from ground, through the contact of relay 26S, winding of relay 262 to battery to interrupter 2&7. Under this condition relay 2i2 is energized from ground on the sleeve, conductor F35, brush e, conductor 253, contact of relay Z, contact 2 of relay 22, contact 3 of relay 23 normal, winding of relay 212 to battery. Since relay 232 is operated, a circuit is not established at this time for relay 29:9 or the release magnet 2st. After an interval of time a release alarm is sounded in the alarm circuit. Relay 436i is operated when a connector is removed from service so that the testing circuit will not receive a false indication during a test of this connector.

What is claimed is:

1. In an automatically operable telephone ofiice, automatic switches including connectors, a connector testing circuit, means in a connector for operating a signal circuit for initiating the operation of said testing circuit and'for indicating the location of said connector to said testing circuitfmeans in said testing circuit responsive to the operation of said signal circuit for connecting said testing circuit with said connector, means in said testing circuit for disconnecting from a connector in use for normal telephone service and means in said testing circuit for releasing a connector held operated but not in use for normal telephone service.

2. In an automatically operable telephone ofce, automatic switches including connectors, a connector testing circuit, means in a connector for operating a signal circuit for initiating the operation of said testing circuit and for indicating the location of said connector to said testing circuit, means in said testing circuit responsive to the operation of said signal circuit for connecting said testing circuit with said connector, means in said testing circuit for disconnecting from said connector when found in use for normal telephone service and means for repeating said test under the control of said signal circuit.

3. In an automatically operable teiephone ofrice, automatic switches including connectors, a connector testing circuit, a trouble indicating circuit, means in a connector for operating said trouble indicating circuit, means in said trouble indicating circut for initiating the operation of said testing circuit and for indicating the location of said connector to said testing circuit, means in said testing circuit responsive to the operation of said trouble indicating circuit for connecting said testing circuit with said connector, means in said testing circuit responsive to voltage polarity of current connected to the calling subscribers line upon the release of the called subscriber for restoring said connector to normal and means in said testing circuit responsite to the voltage polarity of current connected to the calling subscribers line with the receivers of two connected subscribers off their respective switchhooks for disengaging the testing circuit from said connectors.

4. In an automatically operable telephone office, automatic switches including connectors, a connector testing circuit having a step-by-step switch therein, a trouble indicating circuit, means in a connector for operating said trouble indicating circuit, means in said trouble indicating circuit for initiating the operation of said connector testing circuit and for indicating the location of the connector having a trouble condition to said testing circuit, means for connecting said testing circuit switch with said connector, means in said testing circuit responsive to a current from a tone source in a connector for actuating said' testing circuit to disengage the testing circuit switch brushes from said connector, and means to repeatedly test said connector responsive to the continued actuation of said troubled indicating circuit.

5. In an automatically operable telephone office, automatic switches including banks of connector switches, a connector testing circuit having a step-by-step switch therein, a trouble indicating circuit, means in a connector for operating said trouble indicating circuit, means in said trouble indicating circuit for initiating the operation of said testing crcuit and for indicating the bank loca-tion of the connector having a trouble condition to said testing circuit, means for connecting said testing circuit switch with said connectors, means in said testing circuit responsive to current from a source in a connector circuit for disengaging the testing circuit switch brushes from said connector and means in said testing circuit responsive to current from another source in a connector for arresting the advance of said testing circuit switch brushes.

6. In an automatically operable telephone 0fice, automatic switches including banks of connector switches, a connector testing circuit having a step-by-step switch therein, a trouble indicating circuit, means in a connector for operating said trouble indicating circuit, means in said trouble indicating circuit for initiating the operation of said testing circuit and for indicating the bank location of the connector having a trouble condition to said testing circuit, means for connecting said testing circuit switch with said connectors, a vacuum tube circuit in said testing circuit responsive to current from a source in a connector circuit for actuating said testing circuit to disengage the testing circuit switch brushes from said connector and means in said testing circuit responsive to current from another source in a connector for arresting the advance of said testing circuit switch brushes.

7. In an automatically operable telephone ofce, automatic switches including connectors, a connector testing circuit having a step-by-step vswitch therein, a trouble indicating circuit, means for Voperating said trouble indicating circuit, means in said trouble indicating circuit for initiating the operation of said connector testing circuit and for indicating the location of the connector having a trouble condition to said testing circuit, means for connecting said testing circuit switch with said connector, an alternating current source in said connector for indicating a service connection, an amplifying circuit and a rectifying circuit in said testing circuit responsive to said alternating current source for developing a direct current source to actuate said testing circuit for disengaging the testing circuit switch brushes from said connector terminals and for restoring said testing circuit to normal.

8. In an automatically operable telephone ofce, automatic switches including connectors, an 'automatic connector testing circuit having a switch, means for directing said testing circuit switch to the location of particular connectors, means in said testing circuit variably responsive to variable connector circuit conditions, in a connector in use for conversational service between two subscribers, in a connector associated with a subscribers station being actuated by ringing current, in a connector associated with a busy line and in a connector for use for conversational service between a calling subscriber and an intercepting operator, for disassociating said testing circuit from a connector in any one of said circuit conditions, and means responsive to a connector circuit condition in a connector held operated by a calling subscriber after the called subscriber has replaced the receiver for restoring said connector to normal,

9. In an automatically operable telephone ofiice, automatic switches including connectors, a connector switch testing circuit, a switch in said testing circuit having a plurality of sets of terminals in groups, each set being wired to a connector, la signal circuit, means in the connectors of a group for operating said signal circuit, means in said signal circuit responsive to its operation for marking a group of connectors for test, means in said signal circuit for actuating said testing circuit to cause its switch to hunt for said marked group, means in said testing circuit to cause its association with the connectors of said group, means in said testing circuit responsive to varied circuit conditions in a connector in any phase of completing a service connection or which has completed a service connection for disassociating the testing circuit from said connector and causing the test switch to step to the next succeeding connector of the group and means in said testing circuit responsive to a non-service circuit condition in 4a connector for restoring said connector to normal.

10. In an automatically operable telephone ofce, automatic switches including connectors, a connector switch testing circuit, a switch in said testing circuit having a plurality of sets of terminals in groups, each set being wired to a connector, a signal circuit, means in the connectors of a group for operating said signal circuit, means in said signal circuit responsive to its operation for marking a group of connectors for test, means in said signal circuit for actuating said testing circuit to cause its switch to hunt for said marked group, means in said testing circuit to cause said switch to step from one connector to the next connector throughout said group responsive to variable connector circuit conditions, in a connector in use for conversational service between two subscribers, in a connector associated with a subscribers station being actuated by ringing current, in a connector associated with a busy line and in a connector for use for conversational service between a calling subscriber and an intercepting operator, for disassociating said testing circuit from connectors in `any of said circuit conditions and means in said testing circuit responsive to a circuit in a connector held operated by a calling subscriber after the called subscriber has replaced the receiver for restoring said connector to normal.

GEORGE LELAND C'AIN. ELTON SMITH. HAROLD ARTHUR SOUCY. 

